This invention relates to the field of intraluminal guide wires for advancing catheters such as stent delivery catheters, balloon dilatation catheters, atherectomy catheters and the like, within body lumens.
In a typical percutaneous coronary procedure, a guiding catheter having a preformed distal tip is percutaneously introduced into a patient""s peripheral artery, e.g. femoral or brachial artery, by means of a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. For rapid exchange type catheters having a short guidewire receiving lumen within their distal extremities, a guide wire is first advanced by itself through the guiding catheter until the distal tip of the guide wire extends beyond the arterial location where the procedure is to be performed. Then a rapid exchange type catheter, such as described in U.S. Pat. No. 5,061,395 (Yock), is mounted onto the proximal portion of the guide wire which extends out of the proximal end of the guiding catheter which extends outside of the patient. Over the wire type catheters (OTW) have guidewire lumens which extend through the entire length of the catheter and with these types of catheters the guidewire and OTW catheters are advanced together within the guiding catheter until the distal ends thereof are at the distal end of the guiding catheter. The guidewire is then advanced out the distal end of the guiding catheter into the body lumen until the distal end of the guidewire is disposed beyond the procedure site.
In either case, once the guidewire is in place with the distal end distal to the procedure site, the intravascular catheter is then advanced over the guide wire, while the position of the guide wire is fixed, until the operative means on the catheter is disposed within the arterial location where the procedure is to be performed. After the procedure, the intravascular catheter may be withdrawn from the patient or the guide wire repositioned within the coronary anatomy for an additional procedure.
Further details of guide wires, and devices associated therewith for various interventional procedures can be found in U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.); U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams et al.); and U.S. Pat. No. 5,345,945 (Hodgson, et al.) which are hereby incorporated herein in their entirety by reference thereto.
Conventional guide wires for angioplasty, stent delivery, atherectomy and other intravascular procedures usually have an elongate core member with relatively stiff proximal section and a flexible distal section with one or more distally tapered segments. A flexible body member, such as a helical coil or a tubular body of polymeric material, is typically disposed about the distal section of the core member. A shapeable member, which may be the distal extremity of the core member or a separate shapeable ribbon which is secured to the distal extremity of the core member extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding, or an adhesive in the case of polymeric flexible bodies which forms a rounded distal tip. The distal section is flexible and will not damage or perforate the vessel or body lumen through which it is advanced and the portion behind the distal tip is increasingly stiff which better supports a balloon catheter or similar device.
The advancement of an intraluminal catheter over a guide wire may be difficult where intravascular tortuosity, calcification, noncompliance, fibrotic plaque, previously deployed stents or other obstructions are present proximal to the target site or lesion. With the use of conventional guide wires having a core member of longitudinally constant stiffness in their proximal sections, the contact of the guidewire with vessel walls, e.g., adjacent a bend in the vessel, may cause the advancing catheter or other device to impinge or xe2x80x9ccatchxe2x80x9d upon such an obstruction, impeding advancement.
The use of a guide wire of lower stiffness may lessen the friction force of the catheter upon the vessel wall and obstruction, but the reduced stiffness may lead to insufficient xe2x80x9cpushabilityxe2x80x9d and prolapse of the guide wire.
One useful approach to easing advancement of the catheter through proximal obstructions is the use of a guidewire commonly called a xe2x80x9cwiggle wirexe2x80x9d which has a core length that is formed into a plurality of xe2x80x9ckinksxe2x80x9d or undulations where the core length has an S-shape. See for example U.S. Pat. No. 5,007,434 (Doyle et al.) assigned to the present assignee which is incorporated by reference herein in its entirety. When an obstruction is encountered, the portion of the xe2x80x9cwiggle wirexe2x80x9d guidewire having the undulating or S-shaped core segment is alternately advanced and retracted through the catheter distal tip, causing the tip to xe2x80x9cnodxe2x80x9d laterally from side-to-side while the catheter is pushed through the vessel, so as to avoid and bypass the obstruction on the vessel wall. However, the guidewire with the kinked or undulating shape generally results in reduced steerability and control for the guidewire, and may require a larger guidewire lumen in the catheter to accommodate the undulated shape which increases the catheter profile.
The present invention is directed to an guide wire for the deployment of an elongated medical device within a patient""s body lumen. The guidewire includes an elongated core member with a proximal core section, a distal core section more flexible than the proximal core section and a flexible body such as a coil or polymeric tube disposed about and secured to the distal core section. The core member includes an intermediate core section disposed between the proximal core section and the distal core section, which has a plurality of segments or sub-portions which alternate between relatively stiff and relatively flexible contiguous segments or sub-portions along a length of the intermediate core section. A flexible segment between two adjacent stiff segments allow the intermediate core section to articulate when advancing through a tortuous body lumen so that the intermediate section bends discontinuously into discrete portions.
The segments of the intermediate core section are disposed in a linear arrangement and alternate between being relatively rigid or stiff and being relatively non-rigid or flexible, along a significant length of the intermediate core section. Thus, each flexible segment is bounded on each end by a stiff segment to allow articulation between the two stiff segments. When the intermediate core section of the guide wire is advanced into a curved portion or bend in the vessel, the intermediate section as a whole bends to conform overall with the vessel curvature. The flexible intermediate segments are substantially less resistant to bending than the stiff intermediate segments; so as a result most of the bending occurs in the flexible core segments, with the relatively stiff intermediate segments remaining relatively straight or otherwise undeformed and articulating about the flexible segments.
When a catheter is advanced through a body lumen over a conventional guidewire and the leading edge of the catheter engages an obstruction in the wall of the vessel, such as a strut from a previously deployed stent, a ledge of fibrotic plaque, or the like, further advancement of the catheter is impeded. However, utilization of a guide wire having features of the invention will allow the distal tip of the catheter to oscillate o r nod. The oscillation or xe2x80x9cnodxe2x80x9d motion of the catheter""s distal tip causes the distal tip to periodically reduce or eliminate contact with the obstruction while the catheter is pushed through the vessel. To provide the oscillation of the catheter""s distal tip, the intermediate core section lies adjacent and across the obstruction. Either the catheter or the guide wire, or both, may be moved longitudinally to an advanced or a retracted position a sufficient distance so that the distal tip of the catheter has alternating contact with bent flexible intermediate segments and straight stiff intermediate segments which causes the catheter tip to xe2x80x9cnodxe2x80x9d laterally f rom side-to-side. The distal tip of the catheter should oscillate or nod a distance of about 0.1 to about 3 mm, preferably about 0.5 to about 1 mm, in order to avoid or bypass the vessel obstruction.
The intermediate core section of the guidewire should have at least one flexible intermediate core segment with proximally and distally adjacent stiff intermediate core sections so that there is at least one point, preferably about 3 to about 5 points or regions of articulation in the bending of the guide wire between the proximal core section and the distal core section. Usually, not more than about 10 points or regions of articulation are needed. The intermediate core section preferably has multiple adjacent pairs of flexible and stiff intermediate core segments to provide an intermediate core section of sufficient length for convenient manipulation by the physician or other operator as the section is alternately advanced and retracted as described above.
The alternating stiff and flexible characteristics can be provided to the intermediate core segments by dimensional changes or material property changes along the length of the intermediate core section. Dimensional changes to produce a periodically variable stiffness characteristic along the length may be made by centerless grinding or otherwise shaping a selected length of the intermediate core section, or adding bands or sheaths to regions of the core, so as to have a periodically variable stiffness along the core. For a core member of substantially circular cross section, the cross-section of the intermediate section may also be circular, with the radius of the cross section being variable longitudinally along a substantial length of the intermediate core section. The rigidity to bending of both the flexible core segments and stiff segments may be determined by selecting a cross section for each based on material mechanical properties.
The transition of cross-sectional variations along the intermediate core section between the stiff and flexible segments is preferably smooth. For example, the radius of the cross section may vary longitudinally in an undulating pattern, e.g. approximately sinusoidal, so that the intermediate core section has a longitudinal surface contour that is undulating. As the intermediate core section is bent to conform to the curvature of a vessel, the inside surface contour (the contour facing the inside of the bend or curve) will have a curvature which is determined both by the variation in diameter of the core within the intermediate section and by the variable curvature of the axis of the intermediate section.
The alternating sections may be of a range of selected overall lengths, typically from about 0.5 to about 10 cm, preferably about 1 to about 5 cm. The pitch or spacing between like segments, i.e. flexible or stiff segments, may range from about 0.1 to about 10 cm. preferably about 1 to about 2 cm. The lengths and transverse dimensions of the intermediate core segments need not be the same along the length of the intermediate core sections. These dimension may be adjusted to provide the desired variations in stiffness along the length of the intermediate section.
The ratio of the rigidity of the stiff segments relative to the flexible segments is substantially greater than unity, e.g. 1.1 to about 1.7, preferably about 1.3 to about 1.5, and is selected to provide a substantial longitudinal variation in curvature of the intermediate core section, when bent to conform to vessel curvature prevailing in vessels in which it is to be used. For a guidewire in which the variation in stiffness in the intermediate section is due to variations in the diameter of the segments having a circular cross section, and wherein the alternating variation in stiffness from segment to segment is due to variation in cross section diameter as described above, the ratio of the maximum diameter of the stiff intermediate segment to the minimum diameter of the flexible intermediate segment is about 5% to about 75%, preferably about 10% to about 20%. A typical example would be the stiff segment having a maximum diameter of about 0.01 inch (0.25 mm) with an adjacent flexible segment having a diameter of about 0.0075 inch (0.19 mm).
Alternatively, the variation in stiffness of the intermediate section may be provided by longitudinal variation in material properties (e.g., by variable heat treatment or by a variation of materials), or by a combination of variation in cross section and variation in material properties.